Toroidal compressor

ABSTRACT

A rotary machine includes a rotor and a disk-shaped valve that contra-rotate within a cylindrical housing while in non-slipping contact with each other. The rotor includes one or more pistons. In one embodiment of the rotary machine, the valve includes a recess that is shaped epitrochoidally to accommodate the pistons as the pistons pass the valve. Each piston includes a seal that is in sliding contact with the surface of a lining of the recess as the piston passes the valve and that is otherwise in sliding contact with the surface of an inner lining of the housing. The linings and the seal are coated with a polishing composition, so that the seal and the lining are continuously polished as the machine operates. In another embodiment of the rotary machine, the rotor and the valve are shaped to be in constant mutual rolling contact. The rotor and the valve are linked mechanically by a rotor gear, with diagonal teeth, that is rigidly attached to the rotor and by two valve gears, also with diagonal teeth, that engage the rotor gear. One valve gear is rigidly attached to the shaft of the valve. The other valve gear slides along the shaft to positively engage the rotor gear. The rotor and the housing define a toroidal chamber. The pistons and the valve cooperate to define a compression regions in the chamber. When the machine is used as a compressor, as the pistons approach the valve, the air, or other compressible fluid, in the compression region is compressed, until a mechanism such as a throttle valve releases the compressed fluid.

[0001] This is a continuation of U.S. patent application Ser. No. 09/561,945, filed May 1, 2000, which is a continuation in part of U.S. patent application Ser. No. 09/250,239, filed Feb. 16, 1999, which is a continuation in part of U.S. patent application Ser. No. 09/146,362, filed Sep. 3, 1998, which is a continuation in part of U.S. patent application Ser. No. 09/069,545, filed Apr. 30, 1998, which is a continuation in part of U.S. patent application Ser. No. 08/946,986, filed Oct. 8, 1997, which is a divisional application of U.S. patent application Ser. No. 08/743,434, filed Nov. 1, 1996, now U.S. Pat. No. 5,797,366, issued Aug. 25, 1998.

FIELD AND BACKGROUND OF THE INVENTION

[0002] The present invention relates to a toroidal compressor of improved design.

[0003] Berry, in U.S. Pat. No. 2,447,929, teaches an internal combustion engine in which an air-fuel mixture is compressed in a series of tandem toroidal compression chambers, ignited in a “pre-combustion and firing chamber” and allowed to expand to do useful work in a series of tandem toroidal expansion chambers. Each compression chamber, and each expansion chamber, includes a rotor from which projects a piston, and a rotating valve whose rotation is synchronized with the rotation of the rotor and that includes a recess that accommodates the piston as the piston passes the valve. In the compression chambers, the pistons compress air against the valves, and in the expansion chambers, the hot combustion gases push the pistons away from the valves.

[0004] The toroidal compressor design of Berry offers benefits, beyond its application to internal combustion engines, to compressors generally. The unidirectional rotation of the rotor allows high piston velocities in the combustion chambers. The absence of a crankshaft and crank mechanisms eliminates high dynamic loads and reduces the weight of the compressor. In refrigeration applications, the inlets of the compression chambers may be located sufficiently far from the outlets that the temperature distributions in the chambers are stationary. Several compressors may share the same drive shaft.

[0005] Adamovski, in PCT Application US99/19315, which is incorporated by reference for all purposes as if fully set forth herein, teaches a toroidal internal combustion engine that is similar to Berry's, but in which the compression region is defined by the valve, the piston, and/or the combustion/expansion chamber housing, rather than being separate from the combustion and expansion chambers. Adamovski's engine also includes certain other improvements over Berry's engine.

[0006] Edwards, in PCT Application AU93/00171, also teaches an internal combustion engine based on a lobate rotor that rotates within a cylindrical housing. As in Adamovski's engine, the compression and expansion regions are defined by the rotor lobes, the housing, and a radially sliding seal. Combustion takes place external to the housing in separate combustion chambers. The compression and expansion regions are sealed by rotor edge seals in sliding contact with the inner cylindrical surface of the housing and by rotor side face seals in sliding contact with the side plates of the housing.

[0007] Wankel, in U.S. Pat. No. 4,626,182, teaches a single-chamber compressor that is similar in design to the compression chambers of Berry's engine. The rotor has two pistons, and these pistons, as well as the valve recess, are shaped to minimize flow losses due to seal wedging flow and compression.

SUMMARY OF THE INVENTION

[0008] According to the present invention there is provided a rotary machine, including: (a) a housing; (b) a rotor, rotatably mounted within the housing, the rotor and the housing defining between them a toroidal chamber, the rotor including a piston projecting into the toroidal chamber; and (c) a valve, rotatably mounted within the housing, the valve including a circular disk having a recess shaped epitrochoidally relative to the piston so as to accommodate the piston as the piston moves past the valve.

[0009] According to the present invention there is provided a rotary machine, including: (a) a housing having a lining, the lining having a surface; (b) a rotor, rotatably mounted within the housing, the rotor and the housing defining between them a toroidal chamber, the rotor including a piston projecting into the toroidal chamber, the piston including a seal that contacts the surface of the housing lining as the rotor rotates within the housing; (c) a valve, rotatably mounted within the housing, the valve including a circular disk having a recess shaped to accommodate the piston as the piston moves past the valve, the recess having a lining, the lining of the recess having a surface, the piston seal contacting the surface of the recess lining as the piston moves past the valve; and (d) a polishing composition applied to the surfaces and to the seal.

[0010] According to the present invention there is provided a rotary machine, including: (a) a housing; (b) a rotor, rotatably mounted within the housing; (c) a valve, rotatably mounted within the housing and including a valve shaft; (d) a rotor gear, rigidly attached to the rotor and including a plurality of diagonal teeth; and (e) two valve gears in tandem, a first the valve gear being rigidly attached to the valve shaft, a second the valve gear being slidably mounted on the valve shaft, the valve gears including diagonal teeth that engage the diagonal teeth of the rotor gear.

[0011] According to the present invention there is provided a compressor for compressing a fluid, including: (a) a housing; (b) a rotor, rotatably mounted within the housing, the rotor and the housing defining between them a toroidal chamber, the rotor including at least one piston projecting into the toroidal chamber; (c) a valve, movably mounted within the housing, the valve including a circular disk having a recess shaped to accommodate each at least one piston as the each piston moves past the valve, the valve cooperating with the housing and with the rotor to form a compression region wherein the fluid is compressed as each at least one piston approaches the valve; and (d) a mechanism for releasing the fluid from the compression region when a pressure of the fluid exceeds a threshold.

[0012] According to the present invention there is provided a compressor for compressing a fluid, including: (a) a housing; (b) a rotor, mounted within the housing to rotate about an axis of rotation and having an outer surface including at least one portion of variable distance from the axis of rotation including a point of maximum distance; (c) a valve, rotatably mounted within the housing and shaped to maintain rolling contact with the outer surface as the rotor and the valve rotate within the housing, the valve and the rotor cooperating with the housing to form a compression. region, wherein the fluid is compressed, as the point of maximum distance approaches the valve; and (d) a mechanism for releasing the fluid from the compression region when a pressure of the fluid exceeds a threshold.

[0013] According to the present invention there is provided a method of compressing a fluid, including the steps of: (a) providing a compressor including: (i) a housing, (ii) a rotor, rotatably mounted within the housing, the rotor and the housing defining between them a toroidal chamber, the rotor including at least one piston projecting into the toroidal chamber, and (iii) a valve, movably mounted within the housing, the valve including a circular disk having a recess shaped to accommodate each at least one piston as the each piston moves past the valve, the valve cooperating with the housing and with the rotor to form a compression region as each at least one piston approaches the valve; (b) introducing the fluid to the compression region; (c) rotating the rotor so that the piston, that cooperates in forming the compression region, approaches the valve, thereby compressing the fluid; and (d) releasing the compressed fluid from the compression region when a pressure of the compressed fluid exceeds a threshold.

[0014] According to the present invention there is provided a method of compressing a fluid, including the steps of: (a) providing a compressor including: (i) a housing, (ii) a rotor, mounted within the housing to rotate about an axis of rotation and having an outer surface including at least one portion of variable distance from the axis of rotation including a point of maximum distance, and (iii) a valve, rotatably mounted within the housing and shaped to maintain rolling contact with the outer surface as the rotor and the valve rotate within the housing, the valve and the rotor cooperating with the housing to form a compression region as the point of maximum distance approaches the valve, the housing including an exit port that first is isolated from the compression region by the rotor and then is exposed to the compression region as the point of maximum distance approaches the valve; (b) introducing the fluid to the compression region; (c) rotating the rotor so that the point of maximum distance approaches the valve, thereby compressing the fluid; and (d) releasing the compressed fluid from the compression region when a pressure of the compressed fluid exceeds a threshold.

[0015] According to the present invention there is provided a rotary machine including: (a) a housing; (b) a valve, rotatably mounted within the housing; and (c) a rotor, rotatably mounted within the housing so as to maintain rolling contact with the valve, the rotor and the housing defining between them a toroidal chamber, a portion of the rotor extending axially beyond the valve.

[0016] The principal deficiency of prior art rotary compressors is that, over the course of their lifetime, their components tend to become misaligned. This degrades the efficiency of these devices. The present invention includes three improvements over the prior art rotary compressors that address this deficiency.

[0017] First, the shape of the valve recess is optimized relative to the shape of the piston. Specifically, the valve recess is shaped epitrochoidally relative to the piston.

[0018] Second, the piston includes a seal that is urged against the surface of the valve recess to maintain contact with the surface of the valve recess as the piston passes the valve. The piston seal also is urged against the inner surface of the housing to maintain contact with the inner surface of the housing when the piston is not opposite the valve. The piston seal, the valve recess surface and the inner surface of the housing are coated with a polishing composition, to ensure that the wear, that occurs inevitably as the compressor operates, occurs in a controlled fashion, so that the contact area between the piston seal and the valve recess surface always spans the full widths of the piston seal and of the valve recess surface, and so that the contact area between the piston seal and the inner surface of the housing always spans the full widths of the piston seal and of the inner surface of the housing. In a compressor for low temperature applications, the piston seal and the valve recess lining preferably are made of polytetrafluoroethylene, most preferably mixed with graphite and molybdenum disulfide; and the preferred polishing composition is a mixture of molybdenum disulfide and sodium silicate. In a compressor for medium temperature applications, the piston seal and the valve recess lining are made of brass or of a copper-silver alloy, and the preferred polishing composition is a mixture of molybdenum disulfide, graphite and a silicone resin. In a compressor for high temperature applications, the piston seal and the valve recess lining are made of a nickel-based alloy, and the preferred polishing composition is a mixture of molybdenum sulfide and graphite. The piston seal is urged against the valve recess surface and against the inner surface of the housing by centrifugal force as the rotor rotates. Optionally, a mechanism, such as a spring, is provided to urge the piston seal against the valve recess surface and against the inner surface of the housing.

[0019] Third, the rotations of the rotor and the valve are synchronized by a mechanical linkage that includes a rotor gear that is rigidly attached to the rotor and a pair of valve gears in tandem on the shaft whereabout the valve rotates. One valve gear is rigidly attached to the shaft. The other valve gear is free to slide on the shaft, but is linked to the first valve gear so that both valve gears rotate together. Diagonal teeth on the valve gears engage matching diagonal teeth on the rotor gear. A spring, that urges the two valve gears apart, maintains this engagement as the gears rotate.

[0020] Although the present invention is described herein in the context of a rotary compressor, it will be appreciated by those skilled in the art that the principles of the present invention apply to rotary machines generally, including, for example, pumps and motors.

[0021] In another aspect of the present invention, the improvements taught by Adamovski with regard to toroidal internal combustion engines are implemented in a toroidal compressor. As in Adamovski's internal combustion engine, air, or any other compressible fluid, is compressed between the piston and the valve as the piston approaches the valve, while either the rotor or the valve isolates the compressed air from an outlet port in the compressor housing. A mechanism such as a throttle valve releases the air when the pressure of the air reaches a predetermined threshold. In one embodiment of the compressor of the present invention, the recess in the compressor housing, within which the valve rotates, includes a channel for preventing sharp fluctuations in pressure as the piston enters the valve recess. Another embodiment of the compressor of the present invention uses a valve-rotor combination of improved design. The valve and the rotor are shaped to maintain mutual rolling contact throughout the compression cycle. The valve includes a movable member that emerges from the valve as the piston departs from the valve. This movable member serves as an additional seal that defines the chambers of the compressor, and also minimizes suction and turbulence that otherwise would retard the motion of the piston and reduce the efficiency of the compressor.

[0022] The principles of the present invention are applicable to rotary machines that include several rotors, each rotor rotating within a respective cylindrical chamber of a common housing.

[0023] The compressor of the present invention is transformed into a pump by removing the mechanism that releases the fluid from the compression region when the pressure reaches the threshold. As a pump, the device of the present invention may be used to pump either compressible fluids, such as air, or incompressible fluids, such as water. By running a fluid backwards through a device of the present invention configured as a pump, the present invention may be operated as a motor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:

[0025]FIG. 1 is a transverse cross section of a first embodiment of a compressor of the present invention;

[0026]FIG. 2 illustrates the geometrical construction of the valve recess;

[0027]FIG. 3 illustrates a variant of the piston and its seal;

[0028]FIG. 4 is a transverse cross section of a second embodiment of a compressor of the present invention;

[0029]FIG. 5 illustrates two kinds of pistons for the compressor of FIG. 4;

[0030]FIGS. 6A and 6B are enlarged fragmentary transverse cross-sections of a valve and of a compressor housing;

[0031]FIG. 7 is an axial cross-section of the compressor of FIG. 1;

[0032]FIG. 8 shows the mechanical linkage of FIG. 7 in more detail;

[0033]FIG. 9 is a conceptual illustration of the positive engagement of the valve gears with the rotor gear;

[0034]FIG. 10 is a transverse cross section of a third embodiment of a compressor of the present invention;

[0035]FIGS. 11 and 12 are transverse cross sections of a fourth embodiment of a compressor of the present invention

[0036]FIGS. 13 and 14 are partial transverse cross sections of the fourth embodiment with alternative valves;

[0037]FIG. 15 is an axial cross section of a fifth embodiment of a compressor of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] The present invention is of an improved rotary machine that can be used as a compressor.

[0039] The principles and operation of a rotary compressor may be better understood with reference to the drawings and the accompanying description.

[0040] Referring now to the drawings, FIG. 1 is a transverse cross section of a first embodiment 10 of a compressor of the present invention. Within a stationary housing 12 rotates an annular rotor 14. Rotor 14 is rigidly attached to a central rotor shaft (reference numeral 66 in FIG. 7) that is coaxial with rotor 14 and with housing 12. Housing 12 and rotor 14 define between them a toroidal chamber 16. Two pistons 18 project from rotor 14 into chamber 16. On one side of housing 12 is a housing recess 20 that accommodates a disk-shaped valve 22 that rotates within housing 12 in a direction opposite to the direction of rotation of rotor 14. Valve 22 includes a valve recess 24. The outer diameter of rotor 14 is twice the diameter of valve 22. Valve 22 rotates twice for each rotation of rotor 14, so that outer surface 26 of valve 22 and outer surface 28 of rotor 14 do not slide relative to each other at their point of mutual contact. The rotations of rotor 14 and valve 22 are synchronized by a mechanical linkage that is described below.

[0041] Valve recess 24 is shaped to accommodate pistons 18 as pistons 18 pass valve 22. The geometrical construction that defines the shape of valve recess 24 is illustrated in FIG. 2. A circle C₂ of radius r₂ rolls without slipping about a circle C₁ of radius r₁. A point P, on a line segment L that extends radially outward from the center of circle C₂, traces a curve 30 that is called an epitrochoid. With circle C₁ centered at the origin of a Cartesian coordinate system (x,y) as shown, and with the motion of circle C₂ parametrized by an angle α between the x-axis and a line connecting the centers of the circles, the equations of epitrochoid 30 are: $\begin{matrix} {x = {{\left( {r_{1} + r_{2}} \right)\cos \quad \alpha} - {r_{2}{{\lambda cos}\left( {\frac{r_{1} + r_{2}}{r_{2}}\alpha} \right)}}}} \\ {y = {{\left( {r_{1} + r_{2}} \right)\sin \quad \alpha} - {r_{2}{{\lambda sin}\left( {\frac{r_{1} + r_{2}}{r_{2}}\alpha} \right)}}}} \end{matrix}$

[0042] where λ is a parameter that describes how far point P is from circle C₂ along line segment L. In terms of compressor 10, circle C₁ represents valve 22 and circle C₂ represents rotor 14, in a rotating coordinate system fixed to valve 22. The portion of line segment L between the circumference of circle C₂ and point P represents a piston 18 of infinitesimal thickness. The shape of valve recess 24 then is given by the portion of epitrochoid 30 that lies within circle C₁. A real piston 18 has finite thickness, so that the shape of valve recess 24 is not exactly a segment of an epitrochoid; but the shape of valve recess 24, relative to any given shape of piston 18, is constructed similarly: rotate rotor 14 about valve 22 without slipping, and remove the material of valve 22 that would otherwise be in the way of piston 18. The resulting shape of valve recess 24 is termed herein “epitrochoidal relative to piston 18”.

[0043] Housing 12 also includes an inlet port 32 and an outlet port 34. Outlet port 34 is reversibly sealed by a throttle valve 36. As drawn in FIG. 1, rotor 14 rotates clockwise and valve 22 rotates counterclockwise. As a piston 18 approaches valve 22, housing 12, that piston 18, and valve 22 define a compression region 38 wherein a compressible fluid such as air in toroidal chamber 16 is compressed as that piston 18 approaches valve 22. As a piston 18 departs from valve 22, that piston draws in behind itself, via inlet port 32, more fluid that will, in turn, be compressed by the other piston 18. When the pressure of the fluid in compression region 38 reaches a predetermined threshold, throttle valve 36 opens to release the compressed fluid.

[0044] Pistons 18 include seals 40 that maintain sliding contact with an inner surface 44 of housing 12 as rotor 14 rotates and with the surface 42 of valve recess 24 as pistons 18 pass valve 22. Although seals 40 are illustrated in FIG. 1 as inserts in pistons 40, other configurations are possible. FIG. 3 illustrates, in exploded perspective, a variant of piston 18 and seal 40 in which seal 40 is a sheath over piston 18. Seal 40 fits into a groove 46 in rotor 14. Shoulders 48 and 50 of seal 40 are extensions of rims 56 and 58 of rotor 14. A leaf spring 54 between piston 18 and seal 40 urges a contact surface 52 of seal 40 against inner surface 44 of housing 12 and against surface 42 of valve recess 24.

[0045]FIG. 4 is a transverse cross section of a second embodiment 110 of a compressor of the present invention. Within a stationary housing 112 rotates a rotor 114 that is substantially annular but that also includes a central channel 108. Rotor 114 is rigidly attached to a central drive shaft (not shown) that is coaxial with rotor 114 and with housing 112. Two pistons 118 slide within channel 108. On one side of housing 112 is a housing recess 120 that accommodates a disk shaped valve 122 that rotates within housing 112 in a direction opposite to the direction of rotation of rotor 114. Like valve 22, valve 122 includes a valve recess 124. As in compressor 10, valve 122 rotates twice for each rotation of rotor 114, so that outer surface 126 of valve 122 and outer surface 128 of rotor 114 do not slide relative to each other at their point of mutual contact. As rotor 114 rotates, the centrifugal forces induced thereby on pistons 118 urge pistons 118 radially outward. Valve recess 124 is shaped to accommodate pistons 118 as pistons 118 pass valve 122. The radially outward ends of pistons 118 are configured as seals 140 that maintain sliding contact with an inner surface 144 of housing 112 as rotor 114 rotates and with the surface 142 of valve recess 124 as pistons 118 pass valve 122. Compressor 110 also includes an inlet port 132, an outlet port 134 and a throttle valve 136 whose functions are identical to the functions of inlet port 32, outlet port 34 and throttle valve 36 of compressor 10.

[0046]FIG. 5A shows pistons 118 in perspective. Note that the radially outward ends of pistons 118 have essentially the same shape as seal 40 of FIG. 3. FIG. 5B shows an alternative configuration of pistons 118′ for compressor 110. Pistons 118′ are plates that have asymmetric mass distributions, so that the centrifugal forces induced on pistons 118 by the rotation of rotor 114 force pistons 118′ in opposite directions. In the illustrated example of pistons 118′, the asymmetric mass distributions are created by fabricating pistons 118′ with eccentric cavities 106.

[0047]FIG. 6A is an enlarged fragmentary transverse cross section of valve 22, showing that valve recess 24 is lined with a surface lining 60, the outward-facing surface of which is surface 42. Similarly, FIG. 6B is an enlarged fragmentary transverse cross section of housing 12, showing that housing 12 is lined with a surface lining 61, the inward-facing surface of which is surface 44. To surfaces 42 and 44, and to shoulders 48 and 50 and contact surface 52 of seal 40, is applied a thin layer 62 of a solid polishing composition. As contact surface 52 slides past valve recess surface 42 and housing surface 44, the polishing composition continuously polishes contact surface 52, valve recess surface 42 and housing surface 44. This controlled mutual wear of contact surface 52, valve recess surface 42 and housing surface 44 maintains the integrity of the sealing provided by seal 40 over the lifetime of compressor 10.

[0048] In a compressor 10 designed to operate at temperatures up to 250° C., the preferred polishing composition is 20% to 60% molybdenum disulfide, with the remainder being sodium silicate. The preferred material of seal 40 and of linings 60 and 61 is polytetrafluoroethylene with up to 30% graphite and up to 10% molybdenum disulfide added. The preferred material of housing 12, rotor 14, pistons 18 and valve 22 is an aluminum composition based on powdered aluminum and also including 13% to 20% alumina, up to 0.25% iron, up to 0.5% fats and up to 0.1% water. Housing 12, rotor 14, pistons 18 and valve 22 are fabricated by sintering this aluminum composition.

[0049] In a compressor 10 designed to operate at temperatures up to 350° C., the preferred material of housing 12, rotor 14, pistons 18 and valve 22 is cast iron including 3.7% to 3.9% carbon, 2.4% to 2.6% silicon, 0.6% to 0.8% manganese, 0.1% to 0.2% titanium, 0.25% to 0.5% copper and 0.3% to 0.5% molybdenum. One preferred material of seal 40 and linings 60 and 61 is brass having the composition 45% to 60% copper, up to 2% manganese, up to 1% lead, up to 1% iron, with the remainder being zinc. Another preferred material for seal 40 and linings 60 and 61 is a copper-silver alloy including between 15% and 25% silver, up to 6% zinc and up to 8% manganese. The preferred polishing composition is a mixture of 30% to 50% molybdenum disulfide having a particle size less than 10 microns and up to 10% graphite, with the remainder being a silicone resin such as polymethylphenyl siloxane.

[0050] In a compressor 10 designed to operate at temperatures up to 550° C., the preferred material of housing 12, rotor 14, pistons 18 and valve 22 is a nickel-tungsten alloy including 30% to 40% tungsten, 7% to I0 % chromium, up to 2% silicon, up to 2% boron, up to 2% carbon and up to 2% iron. The preferred material of seal 40 and linings 60 and 61 is a nickel-based alloy including up to 6% chromium, up to 3% iron, up to 3% silicon and up to 5% boron. This nickel-based alloy is applied to housing 12 and valve 22 by plasma-jet spraying. As in the 350° C. embodiment, the preferred polishing composition is a mixture of 30% to 50% molybdenum disulfide, having a particle size less than 10 microns, and graphite.

[0051]FIG. 7 is an axial cross-section of compressor 10. Rotor 14 is rigidly attached to a rotor shaft 66, as is a rotor gear 70. Valve 22 is rigidly attached to a valve shaft 68, as is a first valve gear 72. A second valve gear 74, in tandem with valve gear 72, is free to slide along valve shaft 68. Shafts 66 and 68 are mounted in journal bearings (not shown) in housing 12. Pins 76 keep valve gears 72 and 74 in rotational alignment as valve 22 rotates. Conventional seals 64 complete the sealing of chamber 16. The surfaces that slide past seals 64 are lubricated by the molybdenum-sulfide-based polishing compositions described above. Note that rotor 14 straddles valve 22, with rims 56 and 58 of rotor 14 flanking valve 22.

[0052]FIG. 8 is a close-up view of valve gears 72 and 74 and part of rotor gear 70. Diagonal teeth 80 on valve gear 72 and diagonal teeth 82 on valve gear 74 engage with diagonal teeth 78 on rotor gear 70. Teeth 78, 80 and 82 are diagonal in the sense that these teeth are not parallel to the rotational axes of their respective gears. Springs 84 urge valve gears 72 and 74 apart to ensure positive engagement of teeth 80 and 82 with teeth 78. A stop 86 limits the extent to which valve gear 74 slides along valve shaft 68. The spacing between valve gears 72 and 74 and between valve gear 72 and stop 86 is exaggerated in FIG. 8 for clarity.

[0053] Valve gear teeth 80 and 82 are slightly narrower than the spacing between rotor gear teeth 78. FIG. 9 illustrates, conceptually, the positive engagement of teeth 80 and 82 with teeth 78 that is provided by springs 84. FIG. 9A shows the situation with valve gears 72 and 84 next to each other. A valve gear tooth 80 and a valve gear tooth 82 are adjacent to a rotor gear tooth 78A but separated from an adjacent rotor gear tooth 78B. This allows valve gears 72 and 74 to slip relative to each other. Springs 84 push valve gears 72 and 74 apart to produce the situation illustrated in FIG. 9B. Now, valve gear tooth 80 is in contact with rotor gear tooth 78B, valve gear tooth 82 is in contact with rotor gear tooth 78A, and valve gears 72 and 74 do not slip relative to each other as the rotation of rotor 14 on rotor shaft 66 drives the rotation of valve 22 via gears 70, 72 and 74. This positive engagement prevents mutual sliding and backlash of rotor 14 and valve 22.

[0054]FIG. 10 is a transverse cross-section of a third embodiment 210 of a compressor of the present invention, illustrating further aspects of the present invention. Within a stationary housing 212 rotates an annular rotor 214. Rotor 214 is rigidly attached to a central drive shaft (not shown) that is coaxial with rotor 214 and with housing 212. Housing 212 and rotor 214 define between them a toroidal chamber 216. Two pistons 218 project from rotor 214 into chamber 216. On opposite sides of housing 212 are two housing recesses 220 that accommodate two disk-shaped valves 222 that rotate within housing recesses 220 in directions opposite to the direction of rotation of rotor 214. Each valve 222 includes a valve recess 224. The outer diameter of rotor 214 is twice the diameters of valves 222. Valves 222 rotate twice for each rotation of rotor 214, so that the surfaces of valves 222 and of rotor 214 that are in mutual contact do not slide relative to each other. The rotations of rotor 214 and valves 222 are synchronized by mechanical linkages (not shown) similar to the mechanical linkage (rotor gear 70 and valve gears 72 and 74) illustrated in FIGS. 7-9. Valve recesses 224 accommodate pistons 218 as pistons 218 move past valves 222. For this purpose, valve recesses 224 are shaped epitrochoidally with respect to pistons 218, as described above. Alternatively, the matching surfaces of pistons 218 and valve recesses 224 are sections of the surfaces of right circular cylinders, as described by M. L. Novikov in Tooth Gearings with New Engagement, N. A. Zhukovsky High Military Engineering Academy, Moscow, 1958 (in Russian).

[0055] Housing 212 also includes two inlet ports 228 and two outlet ports 230 that are reversibly sealed by throttle valves 231. As drawn in FIG. 10, rotor 214 rotates clockwise and valves 222 rotate counterclockwise. As a piston 218 approaches a valve 222, housing 212, that piston 218 and that valve 222 define a compression region 226 wherein air in toroidal chamber 216 is compressed as that piston 218 approaches that valve 222. As a piston 218 approaches a valve 222, that piston 218 draws in behind itself, via a corresponding inlet port 228, more air that will, in turn, be compressed by the other piston 218. When the pressure of the air in a compression region 226 reaches a predetermined threshold, the corresponding throttle valve 231 opens to release the compressed air.

[0056] Each housing recess 220 also includes a channel 232 that connects to the respective compression region 226. The purpose of channel 232 is to equalize pressure between compression region 226 and valve recess 224, so that the pressure of the compressed air in compression region 226 does not drop suddenly when valve 222 reaches the point in the rotation thereof at which valve recess 224 opens upon compression region 226.

[0057] The operation of compressor 210 is as follows. Rotor 214 rotates clockwise. As pistons 218 sweep through chamber 216, each piston 218 compresses air ahead of itself, in the respective compression region 226 thereof, while drawing more air behind itself into chamber 216 via the respective inlet port 228. When the pressure of the air in a compression region 226 reaches a predetermined threshold, the corresponding throttle valve 231 opens to release the compressed air.

[0058] Removing throttle valves 231 turns compressor 210 into a pump: a fluid (compressible or incompressible) that is drawn into chamber 216 via an inlet port 228 is expelled from chamber 216 via the corresponding outlet port 230. Interchanging the roles of inlet ports 228 and outlet ports 230, i.e., introducing the fluid under pressure into outlet port 230 and allowing the fluid to leave chamber 216 via inlet port 228, turns rotary machine 210 into a motor: the fluid drives the counterclockwise rotation of rotor 214.

[0059]FIGS. 11 and 12 are transverse cross-sections of a fourth embodiment 310 of a compressor of the present invention. Within a substantially cylindrical housing 312 rotates a rotor 314 that is rigidly attached to a coaxial drive shaft 356. Rotor 314 rotates in a clockwise direction. Outer surface 340 of rotor 314 includes portions 378 whose radial distances from the rotational axis of rotor 314 are constant and portions 380 whose radial distances increase monotonically (preferably linearly) away from portions 378 towards apices 319. The portion of rotor 314 that includes surface portions 378 and apices 319 is considered to be a pair of pistons 318. Housing 312 and rotor 314 define between them a toroidal chamber 316. The sealing system of compressor 310 is similar to the sealing system of compressor 10, as illustrated in FIG. 6. In particular, apices 319 of pistons 318 are covered with seals (not shown), similar to seal 40, so as to be in sliding contact with the inner wall of housing 312.

[0060] Housing 312 includes two housing recesses 370, within which rotate valves 372, just as valves 222 rotate within housing recesses 220 of embodiment 210. Unlike valves 222, however, valves 372 are not circular disks. Instead, valves 372 are shaped to maintain rolling contact with outer surface 340 of rotor 314. Specifically, the axial profiles of each valve 372 includes a first arcuate portion 374 and a second arcuate portion 376. Arcuate portion 374 is shaped to maintain rolling contact with outer surface 340 along portions 378 thereof, and arcuate portion 376 is shaped to maintain rolling contact with outer surface 340 along portions 380 thereof, and also along apices 319. FIG. 11 shows arcuate portions 374 in contact with portions 378. FIG. 12 shows arcuate portions 376 in contact with apices 319.

[0061] Housing 312 also includes two outlet ports 354 that are reversibly sealed by throttle valves 355. As shown in FIG. 11, as apices 319 approach valves 372, rotor 314, housing 312 and valves 372 define between them two compression regions 350 wherein air is compressed as apices 319 approach valves 372. When the pressure of the air compressed in compression regions 350 reaches a predetermined threshold, throttle valves 355 open, releasing the compressed air from chamber 316. As in the case of compressor 210, the rotations of rotor 314 and valves 372 are synchronized by mechanical linkages (not shown) similar to the mechanical linkage illustrated in FIGS. 7-9.

[0062] The operation of compressor 310 is as follows. Rotor 314 rotates clockwise. As pistons 318 sweep through chamber 316, each piston 318 compresses air ahead of itself, in the respective compression region 350 thereof, while drawing more air behind itself into chamber 316 via a respective housing inlet port 336. When the pressure of the air compressed in compression regions 350 reaches a predetermined threshold, throttle valves 355 open, releasing the compressed air from chamber 316.

[0063]FIGS. 13 and 14 illustrate a feature of a preferred embodiment of valve 372 that improves the sealing of compression regions 350 and also reduces the suction and turbulence that is created in gap 382 (shown in FIG. 12) between arcuate portion 376 and inner surface 384 of a housing recess 370 just after an apex 319 has passed that housing recess 370. FIG. 13 shows valve 372 and rotor 314 in the same relative position as valve 372 and rotor 314 in FIG. 11. FIG. 14 shows valve 372 and rotor 314 in the same relative position as valve 372 and rotor 314 in FIG. 12.

[0064] Arcuate portion 374 of valve 372 includes a curved movable member 386 that is connected to the rest of valve 372 at a pivot 388. As shown in FIG. 14, while arcuate portion 374 faces rotor 314 and apex 319 approaches and reaches contact with valve 372, portion 380 of outer surface 340 presses movable member 386 against valve 372 so that a first leg 396 of movable member 386 maintains rolling contact with portion 380 and a second leg 398 of movable member 386 is accommodated in a slot 394 in valve 372. As shown in FIG. 13, while arcuate portion 376 faces rotor 314, movable member 386 moves outward, so that apex 390, where legs 396 and 398 meet, is in sliding contact with inner surface 384. As apex 319 moves clockwise past the position illustrated in FIG. 14, departing from valve 372, movable member 386 emerges from slot 394 and apex 390 remains in contact with outer surface 340. After apex 319 has passed housing recess 370, apex 390 contacts inner surface 384 and leg 398 reduces the size of gap 382.

[0065] Usually, the speed of rotation of valve 372 is sufficient to urge movable member 386 outward by centrifugal force, to keep apex 390 in proper contact with outer surface 340 or inner surface 384 as necessary. If necessary, a mechanism such as a leaf spring 392 is used to provide supplemental force to urge movable member 386 outward.

[0066]FIG. 15 is an axial cross section of a fifth embodiment 410 of a rotary machine of the present invention that illustrates further features of the present invention. Embodiment 410 consists of two units similar to embodiment 210, in tandem and driven by a common drive shaft 408. A common housing 412 accommodates two chambers 416 a and 416 b that are similar to chamber 216. Within respective chambers 416 a and 416 b rotate two rotors 414 a and 414 b, both of which are rigidly attached to, and coaxial with, drive shaft 408. The left side of housing 412 accommodates two valves 422 that are similar to valves 222 and that rotate within respective housing recesses in directions opposite to the direction of rotation of rotors 414 and shaft 408. Two similar valves 422 b are accommodated in respective housing recesses in the right side of housing 412. As in embodiment 210, valves 422 rotate twice for each rotation of rotors 414. The rotations of rotors 414 and valves 422 are synchronized by gears 452 and 454.

[0067] Like rotor 214, each rotor 414 includes two pistons 418, of which two (418 a) are shown in FIG. 15. Specifically, rotor 414 a is shown in the position in which pistons 418 a pass valves 422 a and are accommodated in matching recesses in valves 422 a. The pistons of rotor 414 are displaced azimuthally by 90° relative to pistons 418 a, and so do not appear in FIG. 15.

[0068] Substantially annular seals 438 serve to seal off chambers 416 by maintaining sliding contact between cylindrical surfaces 415, of the portions of rotors 414 that extend axially beyond corresponding valves 422, and facing cylindrical surfaces 415 of housing 412. Similarly, lateral seals 443 serve to seal off chambers 416 by maintaining sliding contact between respective surfaces of housing 412 and valves 422.

[0069]FIG. 15 illustrates the following features of the present invention:

[0070] 1. Embodiment 410 includes two rotors 414, each with its own set of valves 422.

[0071] 2. Seals 438 are embedded in, and are rigidly attached to, housing 412, and are in sliding contact with rotors 414. This is in contrast with embodiment 10, in which seals 40 are included in pistons 18 and are in sliding contact with housing 12.

[0072] 3. Seals 443 a are embedded in, and are rigidly attached to, housing 412, and are in sliding contact with valves 422 a. Seals 434 b are embedded in, and are rigidly attached to, valves 422 b, and are in sliding contact with housing 412.

[0073] 4. Pistons 418 a are staggered azimuthally relative to the pistons of rotor 414 b. Preferably, the azimuthal displacement, in degrees, between the pistons of adjacent rotors, is 360/(N₁+N₂), where N₁ is the number of pistons per rotor and N₂ is the number of rotors.

[0074] While the invention has been described with respect to a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of the invention may be made. 

What is claimed is:
 1. A rotary machine, comprising: (a) a housing having a surface; (b) a rotor, rotatably mounted within said housing, said rotor and said housing defining between them a toroidal chamber, said rotor including a piston projecting into said toroidal chamber, said piston including a seal that contacts said surface of said housing as said rotor rotates within said housing; (c) a valve, rotatably mounted within said housing, said valve including a circular disk having a recess shaped to accommodate said piston as said piston moves past said valve, said recess having a surface, said piston seal contacting said surface of said recess as said piston moves past said valve; and (d) a polishing composition applied to said surfaces and to said seal.
 2. The rotary machine of claim 1, wherein said polishing composition includes molybdenum disulfide.
 3. The rotary machine of claim 1, wherein said polishing composition includes graphite.
 4. The rotary machine of claim 1, wherein said polishing composition includes a silicone resin.
 5. The rotary machine of claim 1, wherein said polishing composition includes sodium silicate.
 6. The rotary machine of claim 1, wherein said seal includes at least one material selected from the group consisting of polytetrafluoroethylene, graphite and molybdenum disulfide.
 7. The rotary machine of claim 1, wherein said seal includes polytetrafluoroethylene.
 8. The rotary machine of claim 1, wherein said seal includes brass.
 9. The rotary machine of claim 1, wherein said seal includes an alloy of copper and silver.
 10. The rotary machine of claim 1, wherein said seal includes a nickel-based alloy.
 11. The rotary machine of claim 1, further comprising: (e) a mechanism for urging said seal against said surface of said housing as said rotor rotates within said housing, and against said surface of said valve recess as said piston moves past said valve.
 12. The rotary machine of claim 11, wherein said mechanism includes a spring.
 13. The rotary machine of claim 1, wherein said rotor includes a channel wherein said piston is slidably mounted.
 14. The rotary machine of claim 1, wherein said housing had a lining, said surface of said housing being a surface of said housing lining, and wherein said valve recess has a lining, said surface of said valve recess being a surface of said valve recess lining.
 15. The rotary machine of claim 14, wherein said linings and said seal include at least one material selected from the group consisting of polytetrafluoroethylene, graphite and molybdenum disulfide.
 16. The rotary machine of claim 14, wherein said lining s and said seal include polytetrafluoroethylene.
 17. Th e rotary machine of claim 14, wherein said linings and said seal include brass.
 18. The rotary machine of claim 14, wherein said linings and said seal include an alloy of copper and silver.
 19. The rotary machine of claim 14, wherein said linings and said seal include a nickel-based alloy.
 20. The rotary machine of claim 14, further comprising: (e) a mechanism for urging said seal against said surface of said housing lining as said rotor rotates within said housing, and against said surface of said valve recess lining as said piston moves past said valve. 